Out-haul/down-haul sail control device



Sept. 2, 1969 P. L. VELTMAN 3,464,378

OUTHAUL/DOWNHAUL SAIL CONTROL DEVICE Filed Jan. 26, 1968 43 -INVENTOR PRESTON L. VELTMAN ATTORNEY Unit 3,464,378 OUT-HAUL/DOWN-HAUL SAIL CONTROL DEVICE Preston L. Veltman, 212 Old County Road, Severna Park, Md. 21146 Filed Jan. 26, 1968, Ser. No. 700,791 Int. Cl. B63h 9/04 U.S. Cl. 114-102 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a device designed to be attached to the boom of a sail in order to control sail shape and effectiveness.

The art of sail-shape control is complex. Almost every condition of wind and sea calls for optimizing the particular shape of sail being used. For best results, each increment of the total sail must be trimmed (adjusted) to an optimum angle of attack under any specific situation. To accomplish this objective, several separate adjustment mechanisms are often provided to enable one to tune a sail and boat for best performance. It is old in the art to individually control the out-haul and down-haul tensions on a sail. This invention provides a mechanism for obtaining the desired integrated out-haul/down-haul tension relationship by application of a single force.

The vertical tension on a sail parallel to the mast is known as down-haul tension. Horizontal tension, along the boom, is known as out-haul tension. For optimum sail performance under each condition of sea, boat heading and wind velocity, both out-haul and down-haul tension must be considered. Further, when the wind strength increases with any given sail setting, the sail fabric tends to stretch, thus distorting the sail shape. Normally, as wind strength increases, optimum performance requires increasing both out-haul and down-haul tension. Out-haul tension required is generally relatively greater than the down-haul tension employed. For optimum performance, the ratio of out-haul tension to down-haul tension should generally be increased as 'wind strength increases.

The primary object of this invention is to provide a mechanism to obtain relatively variable out-haul and down-haul tensions through a single point force applied to the mechanism of this invention. A further object is to obtain simultaneous control of out-haul and down-haul tensions. A further objective is to provide a mechanism that can be readily adapted to either hollow booms or other shaped booms, without substantial modification of said booms.

For the purpose of illustration, this discussion is limited to a triangular shaped or Marconi type mail sail. However, in practice, the principles described apply to other boom-attached sails, such as a club jib.

The overall object of sail trimming is to obtain an optimum air foil to produce maximum forward force. To accomplish this, the sail must present a proper aerodynamic shape and angle of approach to the incident air stream, so as to produce maximum forward force with minimum drag. The overall contour and shape of the sail is important, as well as surface smoothness.

The individual effects of out-haul and down-haul tension are readily observable. If a sail has too little down-haul tension, wrinkles will be observed perpendicular to the mast in the luff, or forward section, of the sail. If down- States Patent ice haul tension is too great, the sail will tend to wrinkle parallel to the most near the luff section of the sail. The same phenomena may be observed, relative to the foot of the sail in that section adjacent the boom. If out-haul tension is insufiicient, Wrinkles will be observed perpen dicular to the boom; if out-haul tension is too great, wrinkles will be observed parallel to the boom. A properly made and set sail presents an aerodynamically suitable shape to the wind stream encountered.

The leech of a triangular sail is the trailing edge normally supported, at least in part, by battens. Proper leech shape is dependent upon proper coordination of out-haul and down-haul tensions and main-sheet setting relative to any particular situation of sea, wind and boat heading. Control of the leech set and shape is believed by many to be the most important single criterion of successful sail handling. Absolute and relative out-haul and down-haul tensions are major contributors to proper leech set and shape. This invention provides a mechanical means for obtaining optimum sail shape under a wide range of physical conditions through obtaining coordinated specific control of out-haul and down-haul forces by applying tension at a single point of the device herein described and claimed.

The invention can be more readily understood by reference to the drawings, wherein:

FIGURE 1 is a schematic illustration of a triangular sail set on a mast 7 and boom 8. For purposes of this illustration the tack of the sail 2 is considered fixed on the boom at the location indicated. The head of the sail 1 is considered movable in a vertical direction along the line of force 9. The clew of the sail 3 is considered movable along the line of force 6. If the force along line 9 is insufficient, wrinkles appear in a line perpendicular to the mast 7 as illustrated at 4. If the out-haul tension along line of force 6 is insuflicient, wrinkles appear perpendicular to the foot of the sail, as indicated at 5.

FIGURE 2 schematically shows another triangular sail with the tack 11 fixed on the boom at the point indicated, the head 10, movable along line of force 16, and the clew 12, movable along line of force 15. If the down-haul force indicated at 16 is too great, wrinkles appear parallel to the mast, as illustrated at 13. If the out-haul force at 15 is too great, horizontal wrinkles appear as shown at 14.

FIGURE 3 illustrates two horizontal sections through a sail at two out-haul tension settings. The forward edge of the sail is indicated at 20 and the leech edges at 21 and 23. Locations 22 and 24 indicate the maximum sail deflection from a straight line connecting the luff 20 and leech points 21, 23 in a horizontal plane. This schematic drawing illustrates how the fore and aft location of the maximum draft point can be shifted towards the luff by means of increasing tension on the out-haul, as indicated by moving the leech from location 21 to 23. The out-haul tension is transmitted in part up along the leech of the sail thus contributing to controlling the upper sail contours. It has been established that the optimum position of the maximum draft varies, primarily depending on the heading of the boat and wind velocity. As the heading is more to windward, the position of maximum draft in the sail should generally move forward towards the luff. The exact optimum situation varies from sail to sail and boat to boat. However, it has been found that generally the maximum draft, sometimes referred to as maximum chord, should be located approximately one-quarter to one-third of the distance aft from the mast. It has also been found that as wind strength increases, the depth of the chord should be decreased and the position of maximum draft shifted forwards. This is referred to as a flatter sail.

From the overall standpoint, for any given heading there is an optimum sail setting, insofar as both boom position and relative out-haul and down-haul tensions are concerned. Generally, a relaxed sail is best for ofi-the-wind sailing. This calls for loosening both down-haul and outhaul tensions to obtain a full sail to present an optimum wind-catching surface. When coming to windward, the exact sail shape becomes much more critical and should be adjusted for each heading and wind velocity. The device of this invention is designed to facilitate accomplishing these adjustments by applying a single downward force.

FIGURE 4 schematically illustrates one embodiment of this invention. A triangular sail is shown fixed to the boom at tack position 31, and fixed to the main halyard at 30. A sliding goose-neck is located at 38, such that the boom is free to move up and down, in accord with tension applied to the down-haul at 33. The clew is afiixed to the mechanism of this invention at 32. The out-haul force is transferred around a sheave 37 by means of cable 39 to a second sheave 36. The cable 39 passes downward and connects at 40 to a pivotal arm 34 fixed to the boom at 35. It is readily seen that a force applied downward at 33 will be transmitted equally as an out-haul force at 32 and a down-haul force at 30. In that lever 34 pivots around point 35, it is readily seen that if the downward force applied to the lever arm 34 is moved towards point 35 the resultant force at point 32 can be decreased relative to that obtained at 30. Thus, with the particular mechanism illustrated in FIGURE 4, one can obtain out-haul/downhaul relative forces, ranging essentially from 1 to 1 and to 1.

FIGURE shows an embodiment of this invention so designed to produce a relative out-haul/down-haul force of up to 2 to 1. This is accomplished by incorporating a movable sheave 47 connected to the out-haul cable 53. Points 40A, 41 and 42 define the head, tack and clew of a triangular sail, respectively. The tack of the sail is firmly fixed to the boom at 41, and the clew movably fixed at 42, the head of the sail fixed at 40A. A sliding goose-neck is indicated at 51, such that the boom assembly is free to move in accord with down-haul tension applied at 43. The out-haul cable 53 is connected to the clew at 42 passing around a sheave 48 connected to a movable sheave 47. The end of cable 52 is adjustably anchored by means of a screw and worm-gear assembly 49 and 50, respectively. Cable 52 transmits a horizontal force to movable sheave 47, via tension in the direction of a force at 43 acting around sheave 46. The force at 43 pivots around a point fixed to the boom at 45 via lever arm 44. This assembly, embodying the well known principles of mechanical advantage, permits one to obtain a variable relationship between out-haul and down-haul tension, essentially between the values of 2 to 1 and 0 to 1, depending upon the point along the lever arm, 44, at which a downward force is applied, as illustrated at point 43. For example, if the downward force is applied at 43, a 2 to 1 out-haul/downhaul force relationship is obtained. If the downward force is applied to a point mid-way of the lever arm 44, a 1 to 1 out-haul/down-haul relationship is obtained. Likewise, by the use of multiple moving sheaves, increased mechanical advantage of 3 to 1, or more, can be obtained. The zeropoint screw and worm-gear adjustment, illustrated by 49 and 50, allows one to obtain a primary adjustment of tension on the foot of the sail, here illustrated between points 41 and 42.

The illustration of this invention is not meant to be limiting in any way. It is here intended only to teach and claim a mechanism for obtaining integrated and relatively variable out-haul/down-haul tensions on a sail. It is intended that the assemblage of this device be made in unit form,

4 adaptable to existing booms, either hollow or of other shapes. Also, this invention is not meant to be limited in any way as to the specific mechanism of applying the down ward force to the lever arm of this invention.

I claim:

1. A device for controlling the out-haul and down-haul tensions on a sail according to a predetermined ratio comprising in combination a mast, a boom attached to said mast, said boom being movable upward or downward for adjustment of down-haul tensions, a sail attached to said boom at the tack and to said mast at the head, a cable attached to said sail at the clew for out-haul tension adjustment, means mounted on said boom for transmitting a downward force applied thereto to the clew of said sail as an outward pull, said downward force being simultaneously transmitted as down-haul tension on said sail to provide a predetermined ratio of out-haul and down-haul tensions from the single downward force applied thereto.

2. A device in accordance with claim 1, wherein the means for transmitting the downward force to said sail is a force multiplier comprising a lever pivotably mounted at one end to said boom and at the other end to a cable for transmitting force to the clew of said sail as out-haul tension, said force being applied directly as down-haul tension to said sail, said downward force being variably reflected as out-haul tension depending upon the position along the lever at which said downward force is applied.

3. A device in accordance with claim 2 wherein said force multiplier comprises in combination a lever pivotably mounted on said boom at one end and attached to said cable at the other end, a plurality of fixed and moveable sheaves to multiply said force and transmit same as outhaul tension to said clew, said downward force being directly applied as down-haul tension and variably applied in a predetermined ratio as out-haul tension depending upon the position said single downward force is applied to said lever.

4. A device in accordance with claim 2 wherein said force multiplier comprises a lever pivotably mounted on said boom at one end and attached to said cable at the other end, said cable passing over fixed and at least one moveable sheave to multiply said force, said force being transmitted by a cable attached to the moveable sheave as out-haul tension to said clew, said downward force being directly applied as down-haul tension and variably applied in a predetermined ratio as out-haul tension depending upon the position at which said single downward force is applied to said lever.

5. The method of obtaining optimum sail performance by controlling out-haul and down-haul tensions in a predetermined ratio by the application of a single force comprising applying force downwardly to said sail at the tack and simultaneously translating said force to said sail at the clew as out-haul tension in a predetermined ratio of outhaul to down-haul tension, and varying said ratio in accordance with wind conditions whereby optimum sail configuration is obtained.

6. The device of claim 4, having as an integral part thereof a zero adjustment for out-haul tension.

References Cited UNITED STATES PATENTS TRYGVE M. BLIX, Primary Examiner 

